Ultrasound-assisted rapid and efficient one-pot synthesis of furanyl spirooxindolo and spiroquinoxalinopyrrolizidines by 1,3-dipolar cycloaddition: a green protocol

Reverse orientation in the ultrasound-assisted [3 + 2]-cycloaddition reaction of nitrile imines with 3-formylchromone-Meldrum's acid adducts

The [3 + 2]-cycloaddition reaction of nitrile imines with 2,2-dimethyl-5-[(4-oxo-4H-chromen-3-yl)methylene]-1,3-dioxane-4,6-dione tends to form the reverse-orientation products under ultrasound irradiation in EtOH in the presence of Et₃N. Evidence for the structure of product 5b was obtained from single-crystal X-ray analysis.

Ultrasound-Promoted Synthesis of Spirocyclopropanes from Switchable Starting Materials via Azomethine Ylide [3+2]-Cycloaddition

An ultrasound-promoted green protocol to access a new series of spirocyclopropanes from indeno[1,2-b]quinoxaline derivatives and azomethine ylides, generated in situ from the iodine-catalyzed reaction of acetophenones as well as of 2-methylquinoline with pyridine in the presence of a base, is described. These transformations proceed via a spirocyclopropanation reaction followed by elimination of pyridine. Clear evidence for the structure of a spirocyclopropane-linked indenoquinoxaline derivative was obtained from single-crystal X-ray analysis. The most important feature of this reaction is the fact it forms three stereogenic centers, one of which is quaternary, with excellent selectivity.

1,3-Dipolar Cycloaddition Reactions of Nitrile Oxides under "Non-Conventional" Conditions: Green Solvents, Irradiation, and Continuous Flow

The 1,3-dipolar cycloaddition reactions (DCs) of nitrile oxides (NOs) to alkenes and alkynes are useful methods for the synthesis of 2-isoxazolines and isoxazoles respectively, which are important classes of heterocyclic compounds in organic and medicinal chemistry. Most of these reactions are carried out in organic solvents and under thermal activation. Nevertheless the use of supercritical carbon dioxide (scCO₂ ) and ionic liquids (Ils) as alternative solvents and the application of microwave (MW) and ultrasound (US) as alternative activation procedures have evident advantages from the "Green Chemistry" point of view. The critical discussion on the applications of these "unconventional" activation methods and reaction conditions in the 1,3-DCs of NOs is the objective of the present Review.

The design and green synthesis of novel benzotriazoloquinolinyl spirooxindolopyrrolizidines: antimycobacterial and antiproliferative studies

Herein, we report the design and synthesis of novel series of potent anti-TB and antiproliferative benzotriazoloquinolinyl spirooxindolopyrrolizidines via an expeditious green approach by using ionic liquid ([Bmim]BF₄) under ultrasonication.